Light alloy piston



Oct. 26, 1937. K. s'rEmR' LIGHT ALLOY PISTON Filed June 10, 1935Patented Oct. 26, 1937 UNITED STATES 2,097,049 men-r ALLOY PISTON KarlSteiner, Heilbronn, Germany, assignor to American Lnrgi Corporation, NewYork, N. Y.,

a corporation of New York Application June 10, 1935, Serial No. 25,746

. In Germany July 25, 1934 2 Claims. (Cl. sue-i1) The present inventionrelates to light alloy pistons and more particularly to pistons of thetype in which the effects of heat expansion are reduced or compensatedfor.

5 Heretofore, a great number of various piston structures hasbeensuggested toicompensate for the heat expansion of light alloypistons. It has been proposed to eliminate this diiliculty by separatingthe piston head from the piston sleeve la and using a light metal, forexample aluminum, for the head and a heavy metal for the sleeve.However. the combination of these two metals having widely differentproperties did not solve the outstanding problem'and, as a matter of isfact, has presented new difficulties. It has been 4 also proposed tocast steel strips having a low coeflicient of expansion integral withthe piston skirt or sleeve but neither did this method provide asatisfactory structure. It has been attempted to dispense with a directconnection between the piston sleeve and the piston head by providing a.transversal slot between the same.

and relying only on rib-like reinforcements for the connection of thepiston head to the piston pin bosses. In a structure of this characterthe greater heat expansion of the piston head was.

utilized to expand the piston sleeve in the direction of the piston pinand thereby to approximately maintain the distance. of k the bearingsurfaces of the sleeve constant at all temperatures. In some pistons ofthis type the piston sleeve consisted only of two slipper sections whichhave been connected by means of narrow ribs 5 to the piston pin bosses.In some cases the slipper sections have been extended up to underneaththe piston pin bosses where they have been mparatedby means ,of a slot.All these structures although providing compensation forthe heatexpansion to a certain extent, .had the serious inconvenience that theyhave provided openings of relatively large surface on the piston sleevewhich not only considerably weakened the structure but at the same timealso respective bearing surfaces which remains constant andsubstantially unaffected by changes in the temperature of the piston.

It is another object of the present invention to provide an improvedlight alloy piston which is compensated for changes in the distancebetween the slipper sections and which may beinserted into a cylinderwith a minimum of clearance.

It is a further object of the invention to provide a light alloy pistonwhich has a substantially unbroken sleeve surface and for this reasongreat mechanical strength and good wearing qualities. p

The invention also contemplates to provide a light alloy piston which issimple in structure and easy and inexpensive in manufacture.

Other and further-objects and advantages of the invention will appearfrom the following description taken in conjunction with theaccompanying drawing in which,

Fig. 1 illustrates a. longitudinal sectional view of the pistonembodying the principles of the present invention;

Fig. 2 depicts a cross-sectional view of the piston illustrated in Fig.1 and taken online A-A of Fig. 1;

Fig. 3 shows a longitudinal sectional view of a modified embodiment ofthe present invention.

Broadly stated, according to the principles of my invention I provide aclosed and somewhat resilient piston'sleeve or skirt having asubstantially oval cross-section. I also provide a pair ofslippersections which are arranged on the said skirt diametrically opposite toeach other and are connected thereto by means of a narrow rib extendingalong the full length of the piston skirt. The piston skirt proper isseparated from 'the piston head by means of the conventional transversalslot extending around most of the circumference of the head and isconnected to the head only by means of the two conventional supports orribs joining the piston head to the piston pin bosses which are integralwith the piston sleeve.

The invention will now be. more fully explained to those skilled in theart in conjunction with the accompanying drawing.

Referring more particularly to Figs. 1 and 2 of the drawing, a pistonhead I is separated from the bearing surfaces 1 of the piston-sleeve 6by means of a conventional transversal slot 2. The

- only connection between piston pin bosses 5 and.

piston head I is established {bymeans of supports, or piers, 4.Integrally supported by-supsleeve 6 which in contrast to priorstructures has a closed cross-section of oval character and is closedalso underneath the piston pin bosses The thrust faces of piston sleeveor skirt 6 each' piston skirt or the associated slipper sections. The

expansion of the head will be transmitted to the sleeve by means of thetwo supports 4 whereby the distance between the two piston pin bosses 5will increase, The increased distance between the pin bosses will tendto draw by means of the sleeve 6 also the slipper sections 1 inwardly,by approximately the same amount as they have been expanded by theeffect of the heat. In this manner the slipper sections will maintain asubstantially constant distance between their bearing surfaces at alloperating temperatures and will not .be distorted in shape. a v

As illustrated in Fig. 3, in some cases I prefer to provide a pair ofinclined supports, or piers, 9 passing over into-parallel supports Hi toconnect the piston pin bosses with the bottom of the pis-' I ton head.instead of the straight supports 4' shown in Fig. 1. In view of the factthat this piston is practically identical with the one depicted in Figs.1 and 2, its structure and operation will be readily understood withoutany further explanaover prior light alloy pistons. The piston skirt orsleeve is completely smooth, has no slots opening up thesleeve and bymeans of the narrow ribs 8 supports the slipper sections along the fulllength thereof. -This makes possible to obtain great safe;

ty of operation and increased mechanical strength unattainableheretofore.

, A further important advantage of my improved piston is that the partof .the cylinder sleeve or skirt providing the connection betweenslipper sections and'piston pin bosses is convex towards the outside.This not only Permits utilization of the heat expansion of the pistonhead to stronger expand the piston skirt in the direction of the pistonpin and thereby toforce the slipper sectionslinwards by means of theconnecting ribs but at the same time also provides a resilient sup-2,097,049 ports or piers, 4 is arranged a resilient piston templated.The two very narrow and deep slots between the slipper section and thepiston skirt provide the necessary clearance for the purposes of thisresilient displacement.

It will be also appreciated that the piston ac cording the presentinvention is extremely simple in construction and easy and inexpensivein manufacture. In most cases I prefer to cast a piston blank in whichthe slipper sections are integral with'the piston skirt or sleeve andthe grooves separating same from each other are subsequently provided,for example, by means of milling. Likewise, I prefer to extend thepiston skirt in the blank up to the first piston ringgroove, so that thetransversal slot 2 is provided when the grooves are made. In contrast toprior pistons this considerably simplifies the core necessary for thecasting. K v

The improved piston according to the present invention permitsconsiderable reduction of the clearance between the cylinder wall andthe piston surface. For example, a conventional piston of 10 centimetersin diameter made of an aluminum-silicon alloy having a heat expansioncoeificient of 21 10' necessitated the provision of a clearance of0.10'to 0.15 mm. whereas my improved piston made of the same alloy andhaving bodiments thereof, many variations and modifications are possibleand will suggest themselves to those skilled in the art withoutdeparting from the principles of the invention. All of these variationsand modifications are to be considered as being withinthe true spiritand scope of my invention as described in the present specification andas defined in the appended claims.

I claim:

1. A piston comprising a head and depending skirt of generally ovalcross section, the said skirt being provided with bosses interiorlythereof, the said bosses being connected to the head by depending piers,the said skirt being disconnected fromthe head by two oppositelydisposed slots circumferentially extending between said piers, and eachof the thrust .faces of said skirt com prising a web and a slippersection, the said slipper sections being connected to said web by anelongated vertical rib.

2. A piston comprising a head, a skirt of generally oval cross-sectiondepending from said head, said skirt being provided with bossesinteriorly thereof,.a pair of converging piers for each of said bossesdepending from said head and connected to said bosses, the said skirtbeing disconnected from the head by two oppositely disposed slotscircumferentially extending between said piers, and each of the thrustfaces of said skirt comprising a web and a slipper section, the

said slipper sections being connected to said web by an elongatedvertical rib.

1 STEINER.

